It is known from German Patent Disclosure Document DE-OS No. 29 42 504 to etch copper with a copper (II) chloride-containing etching solution which contains as a sequestering agent an alkali chloride, particularly potassium chloride. Such etching solutions are especially suited for use in fabrication of printed circuit boards. Copper (II) chloride etching solutions containing alkali chloride are preferred over conventional solutions containing hydrochloric acid as a sequestering agent because they have a faster etching speed. Furthermore, such solutions eliminate the problems of handling hydrochloric acid which pollutes the air and causes corrosion damage to the processing equipment. Additionally, such solutions can be used in automated spray machines as well as in an immersion process integrated in an automatic galvanizing machine.
Conventional regeneration of copper (II) chloride etching solutions containing alkali chloride is performed by introducing air into the etching solution, which eliminates the need to charge the solution with hydrogen peroxide. However, oxidation by air requires filtration of the resulting copper (II) hydroxide. Filtration is required to obtain metallic copper. The filtration process includes dissolving the copper (II) hydroxide in acid and then treating with electrolytes. However, the filtration method does not efficiently remove the copper hydroxide necessitating the use of additional procedures to achieve regeneration. Thus, the above conventional procedure does not lend itself to a closed system for regenerating copper containing etching solutions.
It is therefore an object of the invention to provide a method of regenerating copper from a copper (II) choride etching solution containing an alkali chloride as a sequestering agent.
It is another object of the invention to provide a method of regenerating copper from said etching solution which removes only the etched off metal from the etching solution.
It is a further object of the invention to provide an apparatus for regenerating said copper (II) chloride etching solution.